In order to bring a number of products to a specific desired temperature, these products can be placed in a sealable room in which the temperature can be controlled. Possible examples are products such as foodstuffs, which are stored deep-frozen. In order to keep products, such as meat and other perishable foodstuffs, suitable for consumption for a relatively long period, these products are stored at a temperature below the freezing point. In order then to be able to process further or consume these items, these products have to be returned at a specific time to a specific temperature above the freezing point.
Particularly in the case of perishable goods, such as meat, it is extremely important not to overheat these articles during defrosting, but to defrost them extremely gradually. If parts of these products are overheated, these products will keep for a much shorter period, and moreover the taste will be impaired. It takes a very long time to return large pieces of meat, such as carcasses, to a temperature above zero degrees, for example four degrees Celsius, while the ambient temperature while the carcass is being warmed up may not be much higher, for example not above six degrees Celsius. The higher the ambient temperature during defrosting, the quicker the goods will reach the desired temperature but the shorter the time will be that the product then remains suitable for human consumption.
The European patent application EP-A 0 298 063 discloses a tunnel in which a fan is used to maintain a maximum flow of air in the tunnel during the entire thawing process. However, the single fan does not give a uniform air flow, since the air flow will be considerably nearer the fan than at a distance from the fan. The products near the fan will therefor be thawed more quickly than the other products.